The purpose of this project was to examine the relationship between smokeless tobacco use and periodontal status in Navajo Indian adolescents. Two hundred and twenty-six Navajos, ages 14-19, were examined for evidence of gingival bleeding, calculus, pocket depth, gingival recession, attachment loss, and oral leukoplakia. They were also questioned about their use of smokeless tobacco products. Of the subjects (75.4% of the boys and 49.0% of the girls), 64.2% were users of smokeless tobacco. Of the users, 25.5% had leukoplakia. The duration (in years) and frequency of smokeless tobacco use (days per week) were highly significant risk factors associated with leukoplakia. No consistent relationship was observed between the use of smokeless tobacco and gingival bleeding, calculus, gingival recession, or attachment loss, either when comparing users to non-users or when comparing the segment where the tobacco quid was habitually held to a within-subject control segment. These results confirm that smokeless tobacco is significantly related to the etiology of leukoplakia. The results of this project have been published.